Tracker Estimates – Sentinel-3 Altimetry Technical Guide – Sentinel Online
The tracker range is the distance from the satellite to the Earth's surface corrected for instrumental corrections such as USO frequency drift, internal path correction or Doppler correction.
The geophysical corrections are not applied to the tracker range. The AGC (Automatic Gain Control) is the gain applied on-board to the waveforms and corrected for instrumental errors.
The sigma0 scaling factor is used to compute the backscatter coefficient of the waveforms. The sigma0 scaling factor represents a backscatter coefficient for waveform amplitude equal to 1.
| PARAMETER | AGC Corrected Estimate |
| NETCDF NAME | agc_[x1]_[x2] where [x1]: 1 Hz or 20 Hz data rates [x2]: Ku-band or C-band. |
| DESCRIPTION | AGC corrected for instrumental errors (agc_cor_[x1]_[x2])For SAR mode, the correction value is the closest in time to the reference measurement. |
| UNITS | 10-2 dB |
| DATA SET AVAILABILITY | Reduced: none Standard: 1 Hz only Enhanced: all |
| OPERATING MODE AVAILABILITY | LRM and SAR |
| DATA ORIGIN | 1 Hz Ku/C-bands: ALT_COM_AGC_01 algorithm 20 Hz Ku-band: SRAL Level-1B product 20 Hz C-band: SRAL Level-1B product |
| ADDITIONAL INFORMATION | None |
| PARAMETERS RELATED | Number of valid points to compute AGC (agc_num_val_[x1]_[x2]) RMS of the AGC (agc_rms_[x1]_[x2]) AGC validity flag (agc_qual_[x1]_[x2]). Flag indicating the use or not of the 20 Hz estimate of AGC in the computation of 1 Hz estimate. |
| PARAMETER DETAILED DESCRIPTION | ESA's Global Land and Ocean Mission for GMES Operational Services |
| PARAMETER | Scaling Factor for Sigma0 Evaluation |
| NETCDF NAME | scale_factor_[x1]_[x2] [x1]: 1 Hz or 20 Hz data rates [x2]: Ku-band or C-band |
| DESCRIPTION | Scaling factor for backscatter coefficient (sigma0) evaluation. This scaling factor represents the backscatter coefficient for waveform amplitude equal to 1. It is corrected for: *AGC instrumental errors (agc_cor_[x1]_[x2]) *Internal calibration (sig0_cal_[x1]_[x2]) |
| UNITS | 10-2 dB |
| DATA SET AVAILABILITY | Reduced: none Standard: none Enhanced: 20 Hz Ku and 20 Hz C-band only |
| OPERATING MODE AVAILABILITY | LRM and SAR |
| DATA ORIGIN | 1 Hz Ku/C-bands: none 20 Hz Ku-band: SRAL Level-1B product 20 Hz C-band: SRAL Level-1B product |
| ADDITIONAL INFORMATION | None |
| PARAMETERS RELATED | None |
| PARAMETER DETAILED DESCRIPTION | ESA's Global Land and Ocean Mission for GMES Operational Services |
| PARAMETER | Tracker Range Estimate |
| NETCDF NAME | tracker_range_[x1]_[x2] [x1]: 1 Hz or 20 Hz data rates[x2]: Ku-band or C-band |
| DESCRIPTION | LRM mode: tracker range corrected for: USO frequency drift (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2]), Doppler correction (dop_cor_l1b_[x1]_[x2]) SAR mode : reference range corrected for: USO frequency drift (uso_cor_[x1]_[x2]), internal path correction (int_path_cor_[x1]_[x2]) |
| UNITS | 10-4 m. An offset of 700,000m to be added to the value read from the netCDF file. |
| DATA SET AVAILABILITY | Reduced: none Standard: none Enhanced: 20 Hz Ku and C-bands |
| OPERATING MODE AVAILABILITY | LRM and SAR |
| DATA ORIGIN | 1 Hz Ku/C-bands: none 20 Hz Ku-band: SRAL Level-1B product 20 Hz C-band: SRAL Level-1B product |
| ADDITIONAL INFORMATION | None |
| PARAMETERS RELATED | Altitude on-board command (H0) computed with navigation/digital elevation model(h0_nav_dem_[x1]_[x2]). Units are on-board clock counter units (3.125/64x10-9 seconds). This parameter is only available in the enhanced 20 Hz - Ku-band data set. |
| PARAMETER DETAILED DESCRIPTION | ESA's Global Land and Ocean Mission for GMES Operational Services |